Propulsion system for boats

ABSTRACT

A propelling machine ( 2 ) is configured curved- tubular, on a ship bottom ( 1 b), with a front casing ( 12 ) having a suction inlet ( 11 ) opening fore to water, an impeller casing ( 10 ) having an impeller ( 17 ) inscribed thereto, and a rear casing ( 14 ) having a delivery outlet ( 13 ) opening aft to water, and the impeller ( 17 ) is forward and reverse rotatable.

TECHNICAL FIELD

This invention relates to a propulsion system for boats such as a boatto run a shallow, for example, a carrier or a houseboat, or a craftequipped with an auxiliary propulsion system, for example a yacht.

BACKGROUND ART

Japanese Patent Application Laying-Open Publication No. Hei-6-219389 hasdisclosed a propulsion system for a wind-powered sailing boat thatemploys, upon entry into or departure from a port or when in a calm, anauxiliary propulsion system having a propeller projecting from thebottom of the boat. Japanese Patent Application Laying-Open PublicationNo. Hei-6-107280 has disclosed a boat propulsion system of acounter-rotating double-propeller type in which swirling streamsgenerated by a fore propeller are rectified into straight streams by anaft propeller.

Propulsion systems for boats to be propelled by a propeller and steeredwith a helm to change the direction of course like above are allowed tobe relatively simple in arrangement for acquisition of a propellingforce to be great, and adapted for transportation of heavy materials,subject to the provision of a shaft projecting from the bottom of boatin the water for mounting the propeller, which has the followingproblems:

(1) The propeller may bite sands or rock in a shallow, or havestring-like drifting matters bound thereon, with a damage to thepropeller or the shaft.

(2) In the case of a yacht, the propeller shaft may act as a fluidresistance to the water, constituting a hindrance to the travel speed. Adrive for the propeller may have noisy rotation sounds, as it has aclutch disengaged when sailing.

(3) The boat needs to be brought onto the shore for repair orreplacement of the propeller.

To this point, Japanese Utility Model Application Laying-Openpublication No. Hei-6-61695 has disclosed a propulsion system for boats,which has a swirling vortical casing incorporated in a hull, with asuction inlet and a delivery outlet confronting the bottom, and in whichwater is drawn by suction at from the suction inlet, to an impellerinstalled thereabove, where it is pressurized and converted intoswirling streams, which are discharged as jets from the delivery outletto produce a propelling force, while the vortical casing is rotatableabout a vertical axis to change the direction of course, withadvantageous adaptation for travel such as on a shallow.

Propulsion systems for boats with arrangement like above are adapted,without projections from the bottom, for travel on a shallow, and withprovision of the vortical casing turnable to effect backward andtransverse travels, for approach to and departure from a pier, subjectto the following problems:

(4) Pressurized swirling streams fill the casing, to be discharged asjets, needing a conversion from kinetic energy of the impeller to energyfor pressurizing streams to be swirled and a conversion from thepressurizing energy to kinetic energy of jets to be discharged, withlosses of energy decreasing efficiency.

(5) The area effective for horizontal jet discharge is kept from beingincreased in comparison with the casing size, with a low propulsionefficiency in the horizontal direction.

(6) Upon switch between forward and backward travels, an entirety of thecasing integrated with the delivery outlet is turned to change thedirection, which is heavy, and needs the system to be full-scaled.

DISCLOSURE OF THE INVENTION

This invention has been made with the above-noted problems in view, andit is an object to be solved by the invention, to provide a propulsionsystem for boats with an incorporated impeller capable of switch betweenforward and backward travels without turning an impeller casing.

According to an aspect of the invention, in a propulsion system forboats, a propelling machine is configured curved-tubular, on a bottom ofboat, with a front casing having a suction inlet opening fore to water,an impeller casing having an impeller inscribed thereto, and a rearcasing having a delivery outlet opening aft to water, and the impellerinscribed to the impeller casing is forward and reverse rotatable,whereby water drawn by suction from the front casing and pressurizedwater to be discharged as jets from the rear casing are changeable inwater stream directions inside the propelling machine, as the impelleris rotated forward or reverse, allowing for the boat to have a switchedtravel direction between forward travel and backward travel, with agreat propelling force obtainable by discharging jets of pressurizedwater into the water.

The impeller inscribed to the impeller casing may preferably beconfigured as a counter-rotating double impeller comprising a frontimpeller and a rear impeller, whereby a greater propelling force than bya single impeller is obtainable with an improved suction performance dueto water streams in travel and an improved delivery performance due tocounter rotation of double impellers.

The impeller inscribed to the impeller casing may preferably compriseaxial flow blades, whereby extended blade surfaces can exert increasedpressurizing forces on water in forward and reverse rotations.

In particular, as the counter-rotating double impeller has axial flowblades, swirling streams of water pressurized at the front impeller canbe guided onto blade surfaces of the rear casing, with increased push-inpressures, to be converted into straight streams by the rear impeller,where they are additionally pressurized.

The impeller casing and the front casing and the rear casing connectedto front and rear ends of the impeller casing may preferably have flowpaths thereof substantially identical in size of inside diameter,whereby discharge power of pressurized water can be substantiallyequalized between forward rotation and reverse rotation, allowing forthe boat to have a propelling force of forward travel, even in backwardtravel.

The impeller casing may preferably be configured arcuate, and a driveshaft with the impeller fixed thereon may preferably be supported bybearings disposed on front and rear peripheral walls of the impellercasing, whereby the drive shaft with the impeller fixed thereon can beevenly supported, with reduced vibrations.

The impeller casing may preferably be configured cylindrical, and adrive shaft with axial flow blades fixed thereon may preferably besupported by a bearing support connected to a rear end of the impellercasing and a bearing on a side wall of the front casing, wherebyvibrations can be reduced, allowing the propelling machine to becompact, as well.

The suction inlet of the front casing and the delivery outlet of therear casing may preferably have plural rectification vanes,respectively, whereby water streams drawn by suction are guided into thefront casing, and swirling water streams are rectified to be discharged,with an improved propelling performance, while preventing foreignmatters from in flowing. If rectification vanes of the front casing areblocked with foreign matters, the impeller can be reverse rotated towash off the foreign matters blocking the rectification vanes.

The front casing may preferably have a suction flow path inclined fore,and the rear casing may preferably have a delivery flow path inclinedaft, whereby suction of water streams in travel as well as aft dischargeof jets into the water can be performed with an increased propellingforce, allowing an application to a large-scale boat such as a carrieror yacht.

The front casing and the rear casing of the propelling machine maypreferably be connected or fastened at lower ends thereof to fixingflanges, and the fixing flanges may preferably be detachably attached toopenings of the bottom of boat, whereby the structure can be compactwithout projections at the bottom of boat, with possible noisereduction. The propelling machine can be configured as a unit attachableto and detachable from the boat bottom.

The impeller casing may preferably be separable fore and aft, wherebythe impeller casing with the inscribed impeller can be assembled ordisassembled with ease, facilitating the cleaning inside the impellercasing, as well as removal of rope or string-like matters binding on theimpeller.

The impeller casing may preferably be separable into an upper half ofimpeller casing and a rear half of impeller casing, and the drive shaftmay preferably be supported by the upper half of impeller casing,whereby the upper half of impeller casing supporting the shaft of theimpeller can be removed from the propelling machine, facilitatingmaintenance services such as repairing.

An inspection hole may preferably be provided to the impeller casing ina vicinity of the impeller, whereby the impeller casing can beinternally inspected with ease, with possible prevention of damages thatotherwise might occur to the impeller or the like.

A boat-side fronting branch path may preferably be branched from therear casing, to be cooperative with the rear casing to effect a flowpath selection therebetween, whereby transverse propulsion can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevation of a yacht equipped with a propulsion systemaccording to an embodiment of the invention;

FIG. 2 is a partially longitudinally cutaway side view of the propulsionsystem of FIG. 1;

FIG. 3 is a longitudinal sectional view of a propelling machine of thepropulsion system of FIG. 2;

FIG. 4 is an exploded longitudinal sectional view of an impeller casingof the propelling machine of FIG. 3;

FIG. 5 is a bottom view of the propulsion system of FIG. 3;

FIG. 6 is an illustration of a forward-reverse rotation shifter of thepropulsion system of FIG. 3;

FIG. 7 is a longitudinal sectional view of a propulsion system for boatsaccording to another embodiment of the invention;

FIG. 8 is an illustration of a counter-rotating double impeller of thepropulsion system of FIG. 7;

FIG. 9 is a perspective view of a propulsion system for boats accordingto another embodiment of the invention;

FIG. 10 is a longitudinal sectional view of a propulsion system forboats according to another embodiment of the invention;

FIG. 11A to FIG. 11D show a propulsion system for boats according toanother embodiment of the invention, in which FIG. 11A is a plan of thepropulsion system, FIG. 11B is a side view of the propulsion system,FIG. 11C is a section of arrow-indicated portion XIC of FIG. 11B, andFIG. 11D illustrates a flow path selection mechanism of the propulsionsystem; and

FIG. 12 is a hydraulic circuit for forward-reverse rotation shifter.

PREFERRED EMBODIMENTS OF THE INVENTION

There will be detailed below preferred embodiments of the invention,with reference to the accompanying drawings. Like members or elementsare designated by like reference characters.

FIG. 1 shows a yacht Y equipped with an auxiliary propulsion system Apaccording to a first embodiment of the invention, FIG. 2 and FIG. 5 showthe auxiliary propulsion system Ap, and FIG. 3 and FIG. 4 show apropelling machine 2 of the auxiliary propulsion system Ap.

The yacht Y is built with a hull 1 equipped with a single mast 1 m and aset of sails 5 as a principal propulsion system. The hull 1 is equipped,at a bottom 1 b thereof, with a keel 6 disposed aft (on a bow 1 c side)of the mast 1 m, and a helm 4 projecting beneath a stern 1 a, and hasthe auxiliary propulsion system Ap incorporated therein between the mast1 m and the helm 4 and fixed on an upside of the bottom 1 b

The auxiliary propulsion system Ap is made up by a water jet propellingmachine 2, an internal combustion engine 3 for driving the propellingmachine 2, and a forward-reverse rotation shifter 8 installed betweenthe internal combustion engine 3 and the propelling machine 2.

The propelling machine 2 is configured with a drive shaft 9 coupled forconnection to the forward-reverse rotation shifter 8, a multispiral-blade impeller 17 keyed to the drive shaft 9, a impeller casing10 as a water flow path circumscribed to the impeller 17 with a minuteclearance, and a front casing 12 and a rear casing 14 connected to frontand rear ends of the impeller casing 10, respectively, and arranged toopen through the bottom 1 b.

In the auxiliary propulsion system Ap, the internal combustion engine 3drives the propelling machine 2, whereby water is drawn by suction froma fore (or aft) water region and discharged as jets of pressurized waterinto an aft (or fore) water region, giving a propelling force for theyacht Y to travel or run forward (or backward). The course of yacht Ycan be changed by the helm 4.

The yacht Y is propelled to travel with the propelling machine 2 drivenby the internal combustion engine 3, in entry to or departure from aport or when in a calm, or with the set of sails 5 receiving winds, in arace or offshore travel, and steered by the helm 4. This propulsionsystem Ap is applicable also to a carrier or houseboat for travel on ashallow.

The forward-reverse rotation shifter 8 is connected between an outputshaft 7 of the internal combustion engine 3 and the drive shaft 9 of thepropelling machine 2.

As shown in FIG. 3, the propelling machine 2 is configuredcurved-tubular as a combination of the impeller casing 10, which isarranged horizontal above the bottom 1 b at the stern 1 a, and formedcylindrical at an intermediate part and curved at both ends, to beshaped arcuate, the front casing 12, which is connected to one end ofthe impeller casing 10 and has a suction inlet 11 opening to the waterat the bottom 1 b on the fore side, and the rear casing 14, which isconnected to the other end of the impeller casing 10 and has a deliveryoutlet 13 opening to the water at the bottom 1 b on the aft side.

The impeller casing 10 has curved peripheral walls, where bearings 15and 16 are disposed, which bearings 15 and 16 of the impeller casing 10serve for horizontally supporting the drive shaft 9 with the impeller 17fixed thereon.

The impeller 17 thus disposed in the impeller casing 10 is forced torotate forward or reverse, by the internal combustion engine 3 of whichoutput is shifted at the forward-reverse rotation shifter 8. Theimpeller 17 is evenly supported in the intermediate part of the impellercasing 10, with reduced vibrations.

The impeller casing 10 is connected, as shown in FIG. 3, at theintermediate part by flanges 18, 18, where it is separable fore and aft,as shown in FIG. 4. The impeller casing 10 has at both ends thereofflanges 19 and 20 formed thereon to be fastened to flanges 19 and 20formed at upper ends of the front casing 12 and the rear casing 14,respectively, whereby assembly as well as disassembly of the propellingmachine 2 is facilitated.

As shown in FIG. 3, the suction inlet 11 of the front casing 12 isprovided with a plurality of rectification vanes 21 arrayed therein andinclined with their lower ends positioned fore, for guiding, in travel,streams of water to inflow the suction inlet 11 of the front casing 12,with increased push-in pressures. The rectification vanes 21 arearranged parallel, with a screening function to prevent foreign mattersfrom entering the front casing 12.

The delivery outlet 13 of the rear casing 14 also has a plurality ofrectification vanes 22 arrayed therein and inclined with their lowerends positioned aft, for rectifying swirling streams of waterpressurized by he impeller 17 into straight streams to be discharged asrearward jets in a water region on the aft side at the stern 1 b, givinga propelling force for the boat 1 to travel forward.

As shown in FIG. 3 and FIG. 5, the front casing 12 as well as the rearcasing 14 has at the lower end a rectangular fixing flange 23 fittedthereon, which fixing flange 23 is detachably attached to be fixed tothe bottom 1 b. The propelling machine 2 is thus united in a compactstructure, wherein noises are reduced and whereby the fixing as well asremoval of the propelling machine 2 to and from the hull 1 isfacilitated.

FIG. 6 shows the forward-reverse rotation shifter 8 installed betweenthe internal combustion engine 3 and the impeller 17. The gear caserotatably supports an input shaft 24 and an idle shaft 25, which arecoupled or operatively connected with the output shaft 7 of the internalcombustion engine 3. A first gear 27 fixed on the input shaft 24 and asecond gear 26 fixed on the idle shaft 25 mesh with each other, rotatingin opposite directions.

The input shaft 24 and the idle 25 have at their distal ends a firsttransmission gear 29 and a second transmission gear 30 fixed thereon,respectively, which first and second transmission gears 29 and 30 meshwith a drive gear 31 fixed on the drive shaft 9, which is inserted intothe gear case. A forward-propulsion oriented multi-disc clutch 32 isfitted to the input shaft 24, whereto the first transmission gear 29loose-splined on the shaft is hydraulically operatively connected toeffect forward rotation of the impeller 17 on the drive shaft 9.

A backward-propulsion oriented multi-disc clutch 33 is fitted to theidle shaft 24 as well, whereto the second transmission gear 30loose-splined on the shaft is hydraulically operatively connected toeffect reverse rotation of the impeller 17 on the drive shaft 9.

As shown in FIG. 3, the inside diameter of the impeller casing 10 andthose of the front casing 12 and the rear casing 14 are substantiallyidentical in size, so that discharge power of pressurized water jets issubstantially equalized between forward and reverse rotations of theimpeller 17, allowing for the hull 1, even in backward travel, to obtainthe propelling force of forward travel, effecting a fast switchingbetween forward travel and backward travel of the boat.

As an output of the internal combustion engine 3 has a rotationaldirection switched reverse by the forward-reverse rotation shifter 8,water incoming from the delivery outlet 13 of the rear casing 9 at thebottom 1 b is guided by the rectification vanes 22, to be transmitted toan aft end of the impeller 18. Water transmitted to the rear side of theimpeller 18 is pressurized by the impeller 18 in reverse rotation, andresultant swirling streams of water are rectified by the rectificationvanes 21 disposed at the suction inlet 11 of the front casing 12, to bedischarged fore as water jets, of which a propelling force propels thehull 1 to travel backward. In the backward travel, a turning can also bepossible by the helm 4.

FIG. 7 shows a propulsion system Pr1 for boats according to anotherembodiment of the invention. This propulsion system Pr1 has a propellingmachine 2 a provided with a counter-rotating double impeller 34 in animpeller casing 10 a, which is configured as a combination of a frontimpeller 34 a and a rear impeller 34 b fixed on a hollow drive shaft 35and a drive shaft 36, respectively, with the drive shaft 36 coaxiallyinserted in the hollow drive shaft 35. The hollow drive shaft 35, onwhich the front impeller 34 a is fixed, and the drive shaft 36, on whichthe rear impeller 34 b is fixed, are operatively connected to aforward-reverse rotation effecter 37.

In the embodiment Pr1 shown in FIG. 7, a front casing 12 a of thepropelling machine 2 a has a suction flow path A inclined fore, and arear casing 14 a has a delivery flow path B inclined aft, so that alower end of the front casing 12 a is substantially parallel torectification vanes 21 arranged in a suction inlet 11 a, providingstreams of water during travel with increased tendencies to enter thefront casing 12 a from the suction inlet 11 a.

A delivery outlet 13 a at a lower end of the rear casing 14 a issubstantially parallel to rectification vanes 22, so that streams ofwater guided by the rectification vanes 22 of the rear casing 14 a aredischarged aft as jets into the water under the boat bottom 1 b.Designated by reference character 23 a is a fixing flange fastened tothe lower end of the front casing 12 a, as well as of the rear casing 14a.

As shown in FIG. 8, the forward-reverse rotation effecter 37 isconfigured to be accommodated in a gear case 41, with a sun gear 38fixed on a proximal end of a drive shaft 36, a plurality of planet gears39 arranged about the sun gear 38, meshing therewith, and an internaltoothed gear 40 as a ring gear fixed on a proximal end of a hollow driveshaft 35 and engaged for meshing with outer peripheries of the planetgears 39, so that, as the sun gear 38 rotates, the internal gear 40 isreverse-rotated via the planet gears 39, thereby rotating in oppositedirections the hollow drive shaft 35, on which the front impeller 34 ais fixed, and the drive shaft 36, on which the rear impeller 34 b isfixed.

In the propelling machine 2 a provided with the reverse-rotating doubleimpeller 34, inflowing water from the suction inlet 11 a of the frontcasing 12 a is pressurized and converted into swirling streams by thefront impeller 34 a, which are guided onto blade surfaces of the rearimpeller 34 b, which converts them into straight streams, exertingthereon increased push-in pressures, effecting additionalpressurization. Rotational power is energy-converted into pressures atthe counter-rotating double-impeller 34, and high-pressure jets aredischarged into the water from the delivery outlet 13 a of the rearcasing 14 a, whereby the boat is propelled forward, while the course ofboat is turnable by a helm.

The propelling machine 2 a provided with the reverse-rotating doubleimpeller 34 has an increased propelling force, and is adapted, as thepropelling machine 2 a has no projections under the boat bottom 1 b, forsuch applications as to a houseboat with a shallow draft and a shallowtravelling boat.

It is noted that the propelling machine 2 shown in FIG. 3 may as well bemodified to have a counter-rotating double impeller 34 in place of thesingle stage impeller 17.

The forward-reverse rotation effecter 37 coupled for connecttion to thepropelling machine 2 a as shown in FIG. 7 is connected to theforward-reverse rotation shifter 8 direct-coupled with the internalcombiustion engine 3 as shown in FIG. 6, so that rotation of the outputshaft 7 of the internal combustion engine 3 is transmitted via theforward-reverse rotation shifter 8, where the rotation is shifted fromforward to reverse, thereby switching, into mutually opposite rotatoinaldirectoins, the front impeller 34 a and the rear impeller 34 b of thecounter-rotating double impeller 34 that the forward-reverse rotationeffecter 37 operates.

As an output of the internal combustion engine 3 is transmitted via theforward-reverse rotation shifter 8 set to shift the rotation into areverse direction for reverse-rotating the counter-rotating doubleimpeller 34, the rear casing 14 a draws water by suction from thedelivery outlet 13 a submerged under the boat bottom 1 b at the stern 1a, and water transferred to the rear side of the rear impeller 34 b ispressurized and converted into swirling streams by the rear impeller 34b, which are rectified by the front impeller 34 a, to be discharged foreat the suction inlet 11 a of the front casing 12, as jets of pressurizedwater into the water, whereby the boat is propelled backward.

If foreign matters are caught on the rectification vanes 21 at thesuction inlet 11 a of the front casing 12 a, blocking the suction inlet11 a, then the counter-rotating double-impeller 34 can bereverse-rotated for discharging pressurized water streams from insidethe front casing 12 a to wash off the foreign matters blocking thesuction inlet 11 a.

In the embodiment Pr1 shown in FIG. 7, a impeller casing 10 a isconfigured with an inspection hole 42 to enable an inspection into theimpeller casing 10 a, where the counter-rotating double impeller 34 isdisposed.

FIG. 9 shows a propulsion system Pr2 for boats according to anotherembodiment of the invention. This propulsion system Pr2 includes apropelling machine 2 b configured with: an impeller casing 43, which isdivided into an upper casing 43 a as an upper half thereof and a lowercasing 43 b as a lower half thereof, which are joined together byflanges 44, 44; and a drive shaft 9 a supported by bearings 15 a and 16a arranged on a peripheral wall of the upper casing 43 a.

The lower casing 43 b is integrally formed with a front casing 45 and arear casing 46 disposed fore and aft, the front casing 45 and the rearcasing 46 being each connected at lower end thereof to a fixing flange47. The upper casing 43 a is removable for an overhal or replacement ofan impeller 17 or counter-rotating double impeller 34 to be facilitated,as well as for removal of string-like matters binding thereon.

It is noted that the inspection hole 42 of the impeller casing 10 a ofFIG. 7 may preferably be provided to either part of the impeller casing10 divided fore and aft as shown in FIG. 3, or to the upper casing 43 aof the impeller casing 43 divided up and down as shown in FIG. 9.

FIG. 10 shows a propulsion system Pr3 for boats according to anotherembodiment of the invention, in which a propelling machine 48 has afront casing 51 defining a suction flow path A′ inclined fore, and arear casing 53 defining a delivery flow path B′ inclined aft.

The front casing 51 has a suction inlet 50, where a plurality ofrectification vanes 58 . . . are arranged with their lower endsmoderately slanting fore in a curvilinerar form for guiding streams ofrunning water inflowing the suction inlet 50 of the front casing 51, tothereby increase push-in pressures to the impeller casing 49, havingenhanced water pressurizing forces along connected blade surfaces ofaxial flow blades 55.

The rear casing 53 has a delivery outlet 52, where also a plurality ofrectification vanes 59 . . . are arranged with their lower endsmoderately slanting aft in a curvilinerar form for converting swirlingstreams of water pressurized by the axial flow blades 55 into straightstreams, discharging as jets into the water under the stern 1 b, with apropelling force to propel the boat forward.

The front casing 51 as well as the rear casing 53 is connected at thelower end to a fixing flange 96, so that the propelling machine 48 isdetachably attached as a unit to the boat bottom 1 b.

The impeller 17 or 34 inscribed to the impeller casing 10 as shown inFIG. 3 may also preferably be cofigured with axial flow blades forhaving water pressurizing forces substantially equalized between forwardand reverse rotations, with a sufficient increase in water pressurizingforce when the axial flow blades are reverse rotated. In particular, inarrangement of the propelling machine 2 a shown in FIG. 7, as thecounter-rotating double impeller 34 inscribed to the impeller casing 10a is configured with axial flow blades, swirling streams of waterpressurized by the front impeller 34 a can be guided onto blade surfacesof the rear impeller 34 b with increased push-in pressures, so that therear impeller 34 b can additionally pressurize drawn water, whileeffecting conversion into straight streams.

FIG. 11A to FIG. 11D show a propulsion system Pr4 for a yacht Yaccording to another embodiment of the invention, in which FIG. 11A is aplan of the propulsion system Pr4, FIG. 11B is a side view of thepropulsion system Pr4, FIG. 11C is a section of arrow-indicated portionXIC of FIG. 11B, and FIG. 11D illustrates a flow path selectionmechanism of the propulsion system Pr4.

The propulsion system Pr4 is configured with a U-shaped impeller casing62 analogous in arrangement to the impelling machine 2, a set of a frontcasing 66 and a 3-way casing 61 connected vy flanges 76 and 75 to frontand rear ends of the casing 62, respectively, and a set of a rear casing63, a left casing 64, and a right casing 65 connected by flanges 72, 73,and 74 to the 3-way casing 61 and substantially horizontally opening tothe water at a stern 1 c, a left side, and a right side of the yacht,respectively. The rear casing 63, left casing 64, and right casing 65are fixed to a hull 1 at delivery outlets thereof, where respectivepluralities of horizontal rectification plates are arranged. The frontcasing is aanalogous in arrangement at the delivery end to thepropelling machine 2. For driving a single stage impeller 68 or acounter-rotating double impeller 68+79, there is provided a drive shaft67, which also has analogous arrangement in connection with an internalcombustion engine to the case of auxiliary propulsion system Ap. It isnoted that, as illustrated in FIG. 11A, the impeller casing 62 maypreferably be joined at an intermediate part thereof by a flange 71 forconvenient inspection or maintenance.

As shwon in FIG. 11C, the 3-way casing 61 has a flow path selectionvalve 80 incorporated therein for selecting an arbitrary one ofleftward, rearward, and rightward flow paths to thereby propel the yachtY rightward, forward, or leftward.

The arrangement of the embodiment Pr4 may preferably be applied to anyembodiment else.

FIG. 12 show a hydraulic circuit for forward-reverse shifter or clutchapplicable to each embodiment described.

In this hydraulic circuit, as a switching valve 90 is operated by aswitching lever 90 a, the hydraulic pressure is switched between aforward propulsion clutch 91 and a backward propulsion clutch 92, whichare connected to an associated operational part of a forward-backwardpropulsion switching mechanism. In the figure, designated by referencecharacter 93 is a pressure control valve, 94 is a hydraulic pump, and 95is an oil tank.

As will be seen from the foregoing description, in a propulsion systemfor boats according to the invention, as an impeller provided in animpeller casing is driven for rotation by an internal combusiton engine,water is guided from a suction inlet at a boat bottom, alongrectification vanes, to be drawn by suction into a front casing, whileentry of foreign matters such as dust is prevented by the rectificationvanes provided plural in the suction inlet of the front casing.

Then, water inflows the inpeller casing, where it is pressurized by theimpeller, and swirling streams of pressurized water are converted intostraight streams by rectification vanes of a rear casing, so thatswirling power is energy converted into pressures, whereby jets ofpressurized water are discharged aft into the water from a deliveryoutlet at the boat bottom, propelling the boat forward.

If the rectification vanes of the front casing are blocked with foreignmatters, the impeller can be reverse rotated, so that water drawn bysuction from the delivery outlet of the rear casing is discharged aspressurized water jets from the suction inlet of the front casing,washing off the foreign matters blocking the rectification vanes.

The impeller to be prodived in the impeller casing of the propellingmachine may prefearbly comprise a counter-rotating double-impeller, withan improved suction performance due to water streams during travel, andan improved delivery performance due to counter rotation of doubleimpellers, with a greater propelling force than by a single impeller.

The impeller to be inscribed to the impeller casing may preferablycomprise axial flow blades, having substantially equalized waterpressurizing forces, whether forward rotation or reverse rotation, witha sufficient increase in pressurizing force to water due to reverserotating axial flow blades.

In particular, the counter-rotating double impeller may preferablycomprise axial flow blades, so that swirling streams of waterpressurized by a front impeller are guided onto blade surfaces of a rearimpeller, with increased push-in pressures, and converted into straightstreams, with additional pressurization, achieving an increasedcollection efficiency by conversion of rotation energy into pressureenergy.

To propel the boat backward, the impeller is rotated reverse, so thatwater drawn by suction from the delivery outlet of the delivery casingis discharged as jets from the front casing, for backward propulsion,with an amount of pressurized swirling water substantially equalized inthe reverse rotation to that in a forard rotation of the impeller ofaxial flow blades, allowing haste switch between forward travel andbackward travel. For a large-scale vessel with a plurality of propellingmachines disposed at the stern, an impeller at the turning side may bereverse rotated for cooperation with a helm to have a small turningrange. For ispection or maintenance of propelling machine, the impellercasing may be removed, allowing a facilitated overhall or internalcleaning of an impeller installed therein.

A small-scale boat may be lifted above the water surface, allowing arepair of the propelling machine or replacement of consumables on thesea.

The rear casing may be branched to have branch flow paths facing boatsides, for cooperation with the rear casing to enable a flow pathselection therebetween, allowing tranverse propulsion.

Therefore, according to the invention, there is achieved an arrangementin which the direction of water suction by a propelling machine as wellas the discharge direction of pressurized water jets can be switched fora boat to travel forward or backward, with a minimized energy loss forreversing rotatoin of water streams, thus providing an incrasedpropelling force, with a facilitated maintenance.

In other words, a boat or yacht equipped with an impeller in the pastmight have suffered in a shallow, from possible damages to the impelleror an inpeller shaft due to a hitting such as to sands. In a propulsionsystem having a vortical casing equipped inside a boat bottom, with avertical axis,kinetic energy to be given to water by an impeller is onceconverted into pressure energy before re-conversion into kinetic energy,with a great loss in the energy conversion, contrary to the invention inwhich, without such conversion, a front casing of which a suction inletis open in a fore water region and a rear casing of which a deliveryoutlet is open in an aft water region are connected to an impellercasing of which an impeller is rotatable both forward and reverse, withan increased propelling force and possible haste switch between forwardtravel and backward travel of boat.

An impeller inscribed to an impeller casing may preferably be configuredas a counter-rotating double impeller, with a front impeller giving anincreased push-in pressure and a rear impeller for converting swirlingstreams ionto straight streams with additional pressurization, allowingfor the conversion from energy of rotational streams to pressure energy,with a greater propelling force than a single impeller.

The impeller to be inscribed to the impeller casing may preferablyconfigured with axial flow blades, having equalized amounts of swirlingpressurized water in forward rotation and reverse rotation, achieving inbackward travel of boat the propelling force of forward travel.

The propelling machine may preferably have flow paths thereofsubstantially identical in size of inside diameter to achievesubstantially equalized discharge forces of pressurized water, whetherthe impeller is rotated forward or reverse.

The impeller casing may preferably be configured with arcuate front andrear peripheral walls for supporting a drive shaft of the impeller to berotated with reduced vibrations and a shortened shaft length.

A bearing support of the impeller casing formed cylindrical and abearing on a side wall of the front casing may preferably support adrive shaft on which axial flow blades are fixed, allowing the shaftlength to be short, as well as the propelling machine to be compact.

In the propelling machine, the suction inlet of the front casing as wellas the delivery outlet of the rear casing may prefearbly have aplurality of recitification vanes arranged therein for guiding waterstreams under suction and rectifying pressurized swirling streams toimprove propsulsion efficiency, besides possible removal of foreignmatters.

The front casing may preferably have a suction flow path inclined foreand the rear casing may preferably have a delivery flow path inclinedaft, allowing suction of runing water streams during travel and aftdischarge of jets in the water to provide an incerased propelling force.

The font casing as well as the rear casing may preferably be fastened atthe lower end to a fixing flange, achieving a compact arrangementwithout projections at the bottom of boat, allowing for the propellingmachine to be attached to or detached from the bottom, as a unit, withease, so that an inspection or repair thereto can be performed on thesea by lifting the boat.

The impeller casing may preferably be configured separable, allowing forfacilitaetd assembly and disassembly of the impeller casing to which theimpeller is inscribed, facilitating an overhall of the impeller disposedinside the impeller casing, as well as an internal cleaning of thepropelling machine.

An inspection hole may preferably be provided to the impeller casing ina vicinity of the impeller, with a facilitated inspection into theimpeller casing, allowing damages such as to the impeller to beprevented in advance.

The rear casing may preferably be branched to provide a branch pathfacing a boat side, for cooperation with the rear casing to enable aflow path selection therebetween, enabling a transverse propulsion.

INDUSTRIAL APPLICABILITY

According the invention, there is provided a propulsion system for boatswith an incorporated impeller, allowing switch between forward andbackward travels without turning the impeller, with simplified boatequipment.

What is claimed is:
 1. A propulsion system for boats, wherein: apropelling machine is configured curved- tubular, on a ship bottom, witha front casing having a suction inlet opening fore to water, an impellercasing having an impeller inscribed thereto, and a rear casing having adelivery outlet opening aft to water; and the impeller inscribed to theimpeller casing is forward and reverse rotatable; wherein the impellercasing, and the front casing and the rear casing, connected to front andrear ends of the impeller casing, respectively, have flow paths thereinsubstantially identical in size to an inside diameter; and wherein theimpeller casing is separable into an upper half of the impeller casingand a rear half of the impeller casing; and a drive shaft is supportedby the upper half of the impeller casing.
 2. The propulsion system forboats according to claim 1, wherein the impeller inscribed to theimpeller casing is configured as a counter-rotating double impellercomprising a front impeller and a rear impeller.
 3. The propulsionsystem for boats according to claim 1, wherein the impeller inscribed tothe impeller casing comprises axial flow blades.
 4. The propulsionsystem for boats according to claim 1, wherein: the impeller casing isconfigured arcuate; and a drive shaft with the impeller fixed thereon issupported by bearings disposed on front and rear peripheral walls of theimpeller casing.
 5. The propulsion system for boats according to claim1, wherein: the impeller casing is configured cylindrical; and a driveshaft with axial flow blades fixed thereon is supported by a bearingsupport connected to a rear end of the impeller casing and a bearing ona side wall of the front casing.
 6. The propulsion system for boatsaccording to claim 1, wherein the suction inlet of the front casing andthe delivery outlet of the rear casing have plural rectification vanesrespectively, for rectifying water streams to inflow the propellingmachine and preventing foreign matters from inflowing.
 7. The propulsionsystem for boats according to claim 1, wherein: the front casing has asuction flow path inclined fore; and the rear casing has a delivery flowpath inclined aft.
 8. The propulsion system for boats according to claim1, wherein: the front casing and the rear casing of the propellingmachine are connected at lower ends thereof to fixing flanges; and thefixing flanges are detachably attached to openings of the bottom ofboat.
 9. The propulsion system for boats according to claim 1, whereinthe impeller casing is separable fore and aft.
 10. The propulsion systemfor boats according to claim 1, wherein an inspection hole is providedto the impeller casing in a vicinity of the impeller.
 11. The propulsionsystem for boats according to claim 1, wherein a boat-side frontingbranch path is branched from the rear casing, and cooperative with therear casing to effect a flow path selection therebetween.